[RTTY] Skimmer spots dropped at VE7CC cluster node

Mon Oct 5 14:58:01 EDT 2015

Well, Jim, since the RBN distributed 922,012 RTTY spots from 36 Skimmers 
during CQWW RTTY, and since my numbers were based on detailed analysis 
of a half dozen of those, don't you think that the reason *none* of the 
spots of your call were correct might lie in your signal, not RTTY 
Skimmer's decoding?

73, Pete N4ZR
Download the new N1MM Logger+ at
<http://N1MM.hamdocs.com>. Check
out the Reverse Beacon Network at
<http://reversebeacon.net>, now
spotting RTTY activity worldwide.
For spots, please use your favorite
"retail" DX cluster.

On 10/5/2015 8:38 AM, Jim W7RY wrote:
> I disagree Pete.
> My call was never spotted by any skimmer. But it was "incorrectly" 
> spotted 41 times.
>
> Sounds like 100% failure to me.
>
> 73
> Jim W7RY
>
>
>
> -----Original Message----- From: Pete Smith N4ZR
> Sent: Monday, October 05, 2015 4:57 AM
> To: Jim W7RY ; RTTY Contesting
> Subject: Re: [RTTY] Skimmer spots dropped at VE7CC cluster node
>
> Jim, the numbers don't bear that out.  Typical busted calls rates with
> RTTY Skimmer are in the 1.4-1.7 percent range.  It would be nice to get
> them down into the same range as CW Skimmer (< 1 percent), but I can't
> imagine what the technical problems would be.  I am reasonably confident
> that  VE7CC has put his finger on one problem - RTTY signals tend to be
> much more closely "zero beat" (CQer and caller) than CW signals. Also,
> there are many more possible Baudot characters than CW letters,
> increasing the risk of miscopies due to interference.
>
> Another thing that people seem to forget is what I call the "crowd
> effect."  If you have 50 Skimmers copying the same transmission at a
> given time, and each of them has a 1percent error rate, there's a 50
> percent chance that one of the Skimmers will miscopy.
>
> This is where tools like cluster-side filters come into play.  I believe
> that VE7CC and AR Cluster V6/CT1BOH both use similar mathematical
> techniques to sort out the busts from the correct copies. They do work.
>
> It might be interesting to know what the average Signal-to-Noise ratio
> was on the busted spots of your call. There are a large number of
> Skimmers in the eastern US and in Europe, and the "competition" may have
> been a lot louder than you in those "markets" when you were being busted
> a lot.
>
> 73, Pete N4ZR
> Download the new N1MM Logger+ at
> <http://N1MM.hamdocs.com>. Check
> out the Reverse Beacon Network at
> <http://reversebeacon.net>, now
> spotting RTTY activity worldwide.
> For spots, please use your favorite
> "retail" DX cluster.
>
> On 10/5/2015 7:08 AM, Jim W7RY wrote:
>> Probably not. Using FSK generated by DOOK (5 KHZ AFSK) and converted 
>> to FSK
>> from 2-Tone.
>> Icom IC7600
>>
>>
>> What it really looks like is the skimmer software has poor decode. If 
>> you look closely at the busted calls, the calls are very similar. So 
>> more of poor decode than too close to someone. LOTS of busted calls 
>> are off by one letter.
>>
>> Am I calling your baby ugly?  If the shoe fits....
>>
>>
>>
>> Thanks
>> 73
>> Jim W7RY
>>
>>
>> -----Original Message----- From: Pete Smith N4ZR
>> Sent: Monday, October 05, 2015 3:36 AM
>> To: rtty at contesting.com
>> Subject: Re: [RTTY] Skimmer spots dropped at VE7CC cluster node
>>
>> Or conceivably because of less than perfect AFSK (bit jitteror
>> distortion from overdrive?)
>>
>> 73, Pete N4ZR
>> Download the new N1MM Logger+ at
>> <http://N1MM.hamdocs.com>. Check
>> out the Reverse Beacon Network at
>> <http://reversebeacon.net>, now
>> spotting RTTY activity worldwide.
>> For spots, please use your favorite
>> "retail" DX cluster.
>>
>> On 10/4/2015 9:18 PM, Lee Sawkins wrote:
>>> You get busted because you are too close in frequency and call to 
>>> W7RN or
>>> W7DRM and they were there first.
>>>
>>> 73 Lee
>>>
>>> ----- Original Message -----
>>>
>>> From: "Jim W7RY" <w7ry at centurytel.net>
>>> To: "Lee Sawkins" <ve7cc at shaw.ca>, rtty at contesting.com
>>> Cc: dezrat at outlook.com
>>> Sent: Sunday, October 4, 2015 11:41:44 PM
>>> Subject: Re: [RTTY] Skimmer spots dropped at VE7CC cluster node
>>>
>>> So why am I in the busted list 41 times?
>>>
>>> 73
>>> Jim W7RY
>>>
>>>
>>>
>>> -----Original Message-----
>>> From: Lee Sawkins
>>> Sent: Wednesday, September 30, 2015 6:19 PM
>>> To: rtty at contesting.com
>>> Cc: dezrat at outlook.com
>>> Subject: [RTTY] Skimmer spots dropped at VE7CC cluster node
>>>
>>> These links may be interesting to some of you. These are the typical
>>> rejected spots of any CC Cluster.
>>>
>>> RTTY skimmer spots are considered valid if spotted by ONE Skimmer. RTTY
>>> Skimmers are generally more accurate than CW and there are simply not
>>> enough
>>> of them to use 2 or more Skimmers to validate them. CW spots are 
>>> valid if
>>> spotted by 2 or more Skimmers.
>>>
>>> Here is the list of dropped Skimmer spots by the VE7CC-1 cluster.
>>> If you connect to the RBN directly, you will receive all these spots as
>>> well
>>> as the good ones.
>>>
>>> Many times there are two calls in succession that are dropped for RTTY
>>> calls. I am receiving data from both the RBN and DL4RCK for redundancy.
>>> Usually they both spot the same RTTY calls.
>>>
>>> Most columns are self explanatory.
>>>
>>> The number directly before a skimmer call is a quality number. It is 
>>> the
>>> number of times a call has been detected as correct minus the number of
>>> times it is busted. When the number decreases below 5, it is no longer
>>> considered valid. If the active call has not been spotted in 12 
>>> minutes it
>>> is also no longer considered valid. In one place, for 9A1A the quality
>>> number is over 2000. This means 9A1A has been spotted over 2000 
>>> times on
>>> the
>>> same frequency!
>>> "Sysop added" means I have manually added a call to the list because 
>>> it is
>>> busted all the time and is never good.
>>>
>>> http://www.bcdxc.org/ve7cc/ccc/Busted-26-Sep-2015.txt
>>> http://www.bcdxc.org/ve7cc/ccc/Busted-27-Sep-2015.txt
>>>
>>> Lee
>>> _______________________________________________
>>> RTTY mailing list
>>> RTTY at contesting.com
>>> http://lists.contesting.com/mailman/listinfo/rtty
>>>
>>>
>>> _______________________________________________
>>> RTTY mailing list
>>> RTTY at contesting.com
>>> http://lists.contesting.com/mailman/listinfo/rtty
>>>
>>
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